The shaded region consists of 16 congruent squares. If $PQ = 6$ cm, what is the area of the entire shaded region?

[asy]
for(int i = 0; i < 5; ++i)
{

for(int j = 0; j < 2; ++j)

{

filldraw((i,j)--(i+1,j)--(i+1,j+1)--(i,j+1)--(i,j)--cycle,gray,linewidth(2));

}
}

for(int i = 0; i < 2; ++i)
{

for(int j = 0; j < 5; ++j)

{

filldraw((i,j)--(i+1,j)--(i+1,j+1)--(i,j+1)--(i,j)--cycle,gray,linewidth(2));

}
}

draw((2,2)--(5,2)--(2,5)--(2,2)--cycle,linewidth(2));

label("P",(2,5),N);
label("Q",(5,2),E);
[/asy]
Answer: Imagine the square whose diagonal would be PQ.  Clearly, that square would be formed of 9 of the shaded squares.  The formula for the area of a square from its diagonal is $A = \frac{d^2}{2}$, therefore, the area of that imaginary square is 18.  Thus, each smaller shaded square has area 2, making for a total of $\boxed{32\text{ square cm}}$ for the entire shaded area.